Electricity questions

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Electricity question collection

Review Electricity questions for Physics, with correct answers shown and coverage across current, potential difference and resistance; series and parallel circuits; circuit components.

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Question 1

Charge flow is given by \(Q = It\). How much charge passes through a wire when \(3\,\mathrm{A}\) flows for \(10\,\mathrm{s}\)?
  1. \(30\,\mathrm{C}\)
  2. \(300\,\mathrm{C}\)
  3. \(13\,\mathrm{C}\)
  4. \(0.3\,\mathrm{C}\)

Question 2

Ohm's law states \(V = IR\). What potential difference does a \(5\,\mathrm{\Omega}\) resistor have if the current is \(2\,\mathrm{A}\)?
  1. \(10\,\mathrm{V}\)
  2. \(7\,\mathrm{V}\)
  3. \(2.5\,\mathrm{V}\)
  4. \(50\,\mathrm{V}\)

Question 3

Which graph best represents an ohmic conductor?
  1. A straight line through the origin
  2. A curve that flattens as \(V\) increases
  3. A parabola opening downward
  4. A horizontal line

Question 4

Why is a filament lamp's I–V graph curved?
  1. Heating raises the filament's resistance
  2. Heating lowers the filament's resistance
  3. The filament keeps constant resistance
  4. The supply voltage changes the filament material

Question 5

Which equation links power \(P\), potential difference \(V\), and current \(I\)?
  1. \(P = VI\)
  2. \(P = \frac{V}{I}\)
  3. \(P = V + I\)
  4. \(P = \frac{I}{V}\)

Question 6

Which form of electricity supply is used in UK homes?
  1. Alternating current at \(230\,\mathrm{V}\), \(50\,\mathrm{Hz}\)
  2. Alternating current at \(120\,\mathrm{V}\), \(60\,\mathrm{Hz}\)
  3. Direct current at \(230\,\mathrm{V}\)
  4. Direct current at \(50\,\mathrm{V}\)

Question 7

Why use a step-up transformer before the National Grid?
  1. Raise voltage, lower current and reduce cable losses
  2. Raise voltage, raise current and reduce cable losses
  3. Lower voltage, lower current and increase cable losses
  4. Convert alternating current into direct current

Question 8

An appliance rating is \(2\,\mathrm{kW}\). How much energy does it use in \(5\,\mathrm{min}\) (\(300\,\mathrm{s}\))?
  1. \(600\,\mathrm{kJ}\)
  2. \(6\,\mathrm{J}\)
  3. \(60\,\mathrm{kJ}\)
  4. \(6000\,\mathrm{J}\)

Question 9

Charge of \(4\,\mathrm{C}\) flows through a component with \(5\,\mathrm{V}\) across it. How much energy is transferred?
  1. \(20\,\mathrm{J}\)
  2. \(0.8\,\mathrm{J}\)
  3. \(9\,\mathrm{J}\)
  4. \(20\,\mathrm{kJ}\)

Question 10

Why is current the same through series components?
  1. Charge has one path through every component
  2. Charge splits equally between the components
  3. Each component uses part of the current
  4. Potential difference forces a new current after each component

Question 11

In parallel circuits, what is the potential difference across each branch?
  1. The same
  2. Different for each branch
  3. Zero
  4. Twice the supply voltage

Question 12

What is the purpose of a plug fuse?
  1. Melt and break an excessive current
  2. Carry fault current safely to earth
  3. Insulate the user from live parts
  4. Reduce the mains potential difference

Question 13

Why does a double-insulated appliance not need an earth wire?
  1. Two insulating layers prevent a live casing
  2. A metal casing carries fault current to earth
  3. A second fuse keeps the casing neutral
  4. A transformer removes the mains voltage

Question 14

Which equation shows the link between power, current and resistance?
  1. \(P = I^2R\)
  2. \(P = I + R\)
  3. \(P = \frac{I}{R}\)
  4. \(P = IR^2\)

Question 15

Which equation gives the energy transferred by electrical work using power and time?
  1. \(E = Pt\)
  2. \(E = \frac{P}{t}\)
  3. \(E = P + t\)
  4. \(E = P^2 t\)

Question 16

Why can a live wire be dangerous when an appliance switch is open?
  1. It may remain at 230 V relative to earth
  2. It becomes the neutral return path
  3. It carries fault current into the earth wire
  4. It changes the supply into direct current

Question 17

Why are NTC thermistors useful in thermostats?
  1. Resistance decreases as temperature rises
  2. Resistance increases as temperature rises
  3. Resistance stays unchanged as temperature rises
  4. Resistance responds to light instead of temperature

Question 18

When do light-dependent resistors (LDRs) have lower resistance?
  1. When light intensity increases
  2. When light intensity decreases
  3. When they are cooled
  4. When they are stretched

Question 19

Why use a step-down transformer in a domestic supply?
  1. Reduce voltage to the appliance's safe value
  2. Increase voltage for grid transmission
  3. Convert alternating current to direct current
  4. Reduce the supply frequency

Question 20

Which ratio describes an ideal transformer?
  1. \(\frac{V_p}{V_s} = \frac{N_p}{N_s}\)
  2. \(\frac{V_p}{V_s} = \frac{N_s}{N_p}\)
  3. \(V_p V_s = N_p N_s\)
  4. \(V_p = V_s\)

Question 21

What happens to a wire's resistance when its length increases?
  1. It increases
  2. It decreases
  3. It becomes zero
  4. It stays unchanged

Question 22

What happens if one branch of a parallel circuit breaks?
  1. Current continues in the other branches
  2. Current stops in the other branches
  3. Supply voltage divides between the remaining branches
  4. Current reverses in the remaining branches

Question 23

What happens to a metal heating element's resistance as it warms?
  1. It increases
  2. It decreases
  3. It stays unchanged
  4. It first increases then returns to its starting value

Question 24

What does the earth wire do during a fault?
  1. Carries fault current safely to earth
  2. Carries normal current to the appliance
  3. Returns normal current to the supply
  4. Melts and breaks the excessive current

Question 25

Which statement about bulbs in series is true?
  1. The supply potential difference is shared between the bulbs
  2. Each bulb receives the full supply potential difference
  3. Current is used up by the first bulb
  4. Adding more bulbs decreases the total resistance

Question 26

A \(12\,\mathrm{V}\) battery supplies two resistors of \(4\,\mathrm{\Omega}\) and \(6\,\mathrm{\Omega}\) in series. What current flows?
  1. \(1.2\,\mathrm{A}\)
  2. \(2\,\mathrm{A}\)
  3. \(0.5\,\mathrm{A}\)
  4. \(10\,\mathrm{A}\)

Question 27

Which equation links charge, current and time?
  1. (Q = It)
  2. (Q = I/t)
  3. (Q = V/I)
  4. (Q = IR)

Question 28

A 920 W appliance uses a 230 V supply. What current does it draw?
  1. 4 A
  2. 0.25 A
  3. 690 A
  4. 211600 A

Question 29

What is the main electrical behaviour of a diode?
  1. Conducts readily in one direction
  2. Conducts equally in both directions
  3. Changes resistance with light level
  4. Stores charge like a cell

Question 30

What happens to total current when a parallel branch is added at fixed voltage?
  1. It increases because total resistance falls
  2. It decreases because current is shared
  3. It stays unchanged because voltage is fixed
  4. It reverses because the path has changed

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Review Electricity questions for Physics, with correct answers shown and coverage across current, potential difference and resistance; series and parallel circuits; circuit components.

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